A series of new well-defined acidic poly(2,7-fluorene) derivatives have been synthesized by palladium-catalyzed Suzuki couplings. Upon deprotonation (i.e., base doping), these conjugated polymers generate stable polymeric anions counterbalanced by alkali metal cations. The resulting polymeric salts exhibit interesting conducting properties. For instance, base-doped poly[2,7-(9,9-dioctylfluorene)-alt-2,7-((4-hexylphenyl)fluorene-9-carbonyl)] exhibits an electrical conductivity of 10(-2)-10(-3) S/cm in air, at room temperature. In all these polymeric systems, a strong polarization of the electrical conduction is observed which seems to indicate a significant ionic transport. These electrical properties confirm the good potential of these novel acidic fluorene-based pi-conjugated polymers for the development of various electrical and electrochemical solid-state devices.